I've checked out those holes for the A/C and they don't vent into the van unless the box isn't sealed properly, they just suck air from below thru the unit and out the side vent so shouldn't be venting or dragging dust in when going down the road.
If they played with your shower they could have stuffed the seal on the wheel arch was all I was thinking.
Yes it's behind why?
If they played with your shower they could have stuffed the seal on the wheel arch was all I was thinking.